A miniature scanning electron microscope for investigation of the interior surface of a superconducting Nb radiofrequency accelerating cavity

A miniature scanning electron microscope with an electron beam diameter ∠1 μm has been constructed for high resolution examination at room temperature of the interior surface of a superconducting Nb radiofrequency accelerating cavity. Various objects and surface structures were observed, some of which could be correlated with lossy regions or ’’hot spots’’ detected previously on the outside surface during cavity operation at ?4.2 K by a chain of carbon resistors. No internal surface features were observed which could conclusively be correlated with field emitting electron sources.